Build a Custom Watched Field
This tutorial will show you how I build my custom [Watched Percent] field, which I use throughout Media Center for display of Watched/Not-Watched Status. It displays it using a combination of checkmarks (for fully watched files) and percentages watched, using custom percentage ranges. Now that we can easily change [Number Plays] (as of MC 19.0.90), it is easy to reset this special Watched status indicator, by simply clearing [Number Plays].
For a discussion of why this logic was used, and how it was built, see this thread.
For the tutorial itself, see: